In recent years, a novel set of wireless technologies termed Low-Power Wide-Area (LPWA) has garnered significant attention from both industry and media. LPWA technologies, especially suited for long-range and battery-operated endpoints, create new revenue prospects for both service providers and organizations exploring IoT solutions.
LoRa was originally a modulation technique for the physical layer. The technology, optimized for long-range, bidirectional communication and minimal battery consumption, progressed from physical layer to a wider framework with the establishment of the LoRa Alliance.
Semtech LoRa serves as a Layer 1 PHY modulation technology and is accessible via several chipset manufacturers. The LoRa Alliance employs the name LoRaWAN to distinguish its architecture and specifications, which delineate end-to-end LoRaWAN communications and protocols, from the physical layer modulation known as LoRa.
The Figure presents a comprehensive overview of the LoRaWAN layers. This chart illustrates that Semtech oversees the PHY layer, whilst the LoRa Alliance manages the MAC layer and regional frequency bands.
Physical Layer
LoRaWAN regional specifications use the main unlicensed sub-GHz frequency bands of 433 MHz, 779–787 MHz, 863–870 MHz, and 902–928 MHz, with regional profiles for a subset of the 902–928 MHz bandwidth.
LoRa gateways, deployed as the center hub of a star network architecture, use multiple transceivers and channels to demodulate multiple channels simultaneously. They serve as a transparent bridge for data relay between endpoints using a single-hop wireless connection.
The data rate in LoRaWAN varies depending on frequency bands and adaptive data rate (ADR), which manages data rate and radio signal for each endpoint. Endpoints close to gateways with good signal values transmit at the highest data rate, enabling shorter transmission time and lowest transmit power, while those at the edge of the link budget communicate at the lowest data rate and highest transmit power.
MAC Layer
The LoRaWAN specification defines the MAC layer, which classifies LoRaWAN endpoints to optimize battery life and ensure downstream communications.
The LoRaWAN specification outlines three classes of LoRaWAN devices: Class A, Class B, and Class C. Class A is optimized for battery-powered nodes, allowing bidirectional communications. Class B is experimental and requires additional receive windows, while Class C is adapted for powered nodes.
LoRaWAN messages have a PHY payload consisting of a 1-byte MAC header, a variable-byte MAC payload, and a 4 bytes MIC. The MAC payload size depends on the frequency band and data rate, with a range of 59 to 230 bytes for the 863-870 MHz band and 19 to 250 bytes for the 902-928 MHz band.
In version 1.0.x, LoRaWAN uses six MAC message types: join request and join accept, unconfirmed data up/down, and confirmed data up/down. Uplink messages are sent from endpoints to the network server and relayed by one or more LoRaWAN gateways, while downlink messages flow from the network server to a single endpoint and relayed by only a single gateway. Multicast over LoRaWAN is being considered for future versions.
LoRaWAN wireless technology is a unified, single standard for seamless interoperability in LPWANs, which are crucial for implementing new devices on IoT networks.
Managed by the LoRa Alliance, LoRaWAN covers longer distances with varying data rates and relies on gateways to bridge endpoints to network servers. It offers AES authentication and encryption at two separate layers.
Unlicensed LPWA technologies present new opportunities for implementing IoT infrastructures, solutions, and use cases for private enterprise networks, broadcasters, and mobile and non-mobile service providers.
The rapidly growing ecosystem of endpoints will be the tie-breaker between various LPWA technologies and solutions. Private enterprises will benefit from roaming capabilities between private and public infrastructures, similar to Wi-Fi infrastructures. LoRaWAN and other LPWA technologies are expected to grow as more interconnected devices are needed.
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